Placebos Use Pot Receptor

Some pain-relief placebos work in part by activating a cannabinoid receptor, stimulating the same pathway as marijuana.

By Tia Ghose | October 5, 2011

FLICKR, E-MAGINE ART

It’s well known that a placebo can relieve pain, but how such non-active ingredients can have such a positive effect has long stumped scientists. Now, new researchers suggests that placebos may help ease a patient’s pain by activating cannabinoid receptors, which are also targeted by marijuana, according to a study published October 2(Sunday) in Nature Medicine.

Researchers can give subjects an opioid prior to wrapping their arm with a painfully tight tourniquet. Thereafter, volunteers can tolerate pain longer when given a placebo instead of drugs on follow-up days, presumably because they’ve been primed to expect pain relief from the drug. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as iburprofen can also be used as a primer to induce this placebo-pain relief effect.

In the new study, researchers gave volunteers an NSAID prior to a painful stimulus, followed by rimbonant, which blocks the activation of a cannabinoid receptor, on subsequent days. Volunteers who received rimbonant on the placebo days experienced no pain relief, suggesting that part of the placebo effect was working via the cannabinoid pathway, and that blocking the pathway abolished the effect, Wired Science reported. When researchers combined rimbonant with an opioid, the placebo still quieted pain, suggesting that the opioid placebo effect works through a different mechanism.

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"When researchers combined rimbonant with an opioid, the placebo still quieted pain, suggesting that the **opioid placebo** effect works through a different mechanism"Â I think it's called the OPIOID RECEPTOR.Â OK... I misread the sentence at first; it sounds like the researchers put an opioid in the placebo.Â But seriously,It is possible that the placebo somehow activates the opioid receptor pathways following treatment with an opioid.Â Acetaminophen, although not an NSAID, has similar pharmacologic properties to ibuprofen (antipyretic, analgesic) - it is thought/known that acetaminophen works via cannabinoid pathways to exert its effect.Presuming that ibuprofen works via cannabinoid pathways, much like acetaminophen does, would explain why rimbonant blocked that effect. (this activity being in addition to the well known COX inhibition pathways)Â All that being said, opioids do not work via cannabinoid pathways but via opioid receptors.Â If the initial treatment is with an opioid, then the patient may be "primed" to have an opioid response when placebo is given, much like the patient is "primed" to have a cannabinoid response after treatment with ibuprofen.Â This would explain why rimbonant blocks pain relief in the ibuprofen arm, and not in the opioid arm.Â A way to test this theory would be to perform the test using a naloxone (opioid antagonist) placebo following ibuprofen or opioid "priming."Â If my "theory of priming" is correct, naloxone would block pain relief following opioid treatment, but have no effect following ibuprofen treatment (i.e. show the opposite results of the rimbonantÂ trial).If such a trial has been performed, then it would be a useful comparison.Â If not, then I think performing such a trial would be complementary to the trial discussed in the article.

"When researchers combined rimbonant with an opioid, the placebo still quieted pain, suggesting that the **opioid placebo** effect works through a different mechanism"Â I think it's called the OPIOID RECEPTOR.Â OK... I misread the sentence at first; it sounds like the researchers put an opioid in the placebo.Â But seriously,It is possible that the placebo somehow activates the opioid receptor pathways following treatment with an opioid.Â Acetaminophen, although not an NSAID, has similar pharmacologic properties to ibuprofen (antipyretic, analgesic) - it is thought/known that acetaminophen works via cannabinoid pathways to exert its effect.Presuming that ibuprofen works via cannabinoid pathways, much like acetaminophen does, would explain why rimbonant blocked that effect. (this activity being in addition to the well known COX inhibition pathways)Â All that being said, opioids do not work via cannabinoid pathways but via opioid receptors.Â If the initial treatment is with an opioid, then the patient may be "primed" to have an opioid response when placebo is given, much like the patient is "primed" to have a cannabinoid response after treatment with ibuprofen.Â This would explain why rimbonant blocks pain relief in the ibuprofen arm, and not in the opioid arm.Â A way to test this theory would be to perform the test using a naloxone (opioid antagonist) placebo following ibuprofen or opioid "priming."Â If my "theory of priming" is correct, naloxone would block pain relief following opioid treatment, but have no effect following ibuprofen treatment (i.e. show the opposite results of the rimbonantÂ trial).If such a trial has been performed, then it would be a useful comparison.Â If not, then I think performing such a trial would be complementary to the trial discussed in the article.

"When researchers combined rimbonant with an opioid, the placebo still quieted pain, suggesting that the **opioid placebo** effect works through a different mechanism"Â I think it's called the OPIOID RECEPTOR.Â OK... I misread the sentence at first; it sounds like the researchers put an opioid in the placebo.Â But seriously,It is possible that the placebo somehow activates the opioid receptor pathways following treatment with an opioid.Â Acetaminophen, although not an NSAID, has similar pharmacologic properties to ibuprofen (antipyretic, analgesic) - it is thought/known that acetaminophen works via cannabinoid pathways to exert its effect.Presuming that ibuprofen works via cannabinoid pathways, much like acetaminophen does, would explain why rimbonant blocked that effect. (this activity being in addition to the well known COX inhibition pathways)Â All that being said, opioids do not work via cannabinoid pathways but via opioid receptors.Â If the initial treatment is with an opioid, then the patient may be "primed" to have an opioid response when placebo is given, much like the patient is "primed" to have a cannabinoid response after treatment with ibuprofen.Â This would explain why rimbonant blocks pain relief in the ibuprofen arm, and not in the opioid arm.Â A way to test this theory would be to perform the test using a naloxone (opioid antagonist) placebo following ibuprofen or opioid "priming."Â If my "theory of priming" is correct, naloxone would block pain relief following opioid treatment, but have no effect following ibuprofen treatment (i.e. show the opposite results of the rimbonantÂ trial).If such a trial has been performed, then it would be a useful comparison.Â If not, then I think performing such a trial would be complementary to the trial discussed in the article.